While camera technology allows images of humans to be recorded, computers may have difficulty using such images to accurately assess how a human is moving within the images. Recently, technology has advanced such that some aspects of a human's movements may be interpreted with the assistance of special cameras and tracking tags. For example, an actor may be carefully adorned with several tracking tags (e.g., retro-reflectors) that can be tracked with several cameras from several different positions, Triangulation can then be used to calculate the three-dimensional position of each reflector. Because the tags are carefully positioned on the actor, and the relative position of each tag to a corresponding part of the actors body is known, the triangulation of the tag position can be used, to infer the position of the actor's body. However, this technique requires special reflective tags, or other markers, to be used.
In science fiction movies, computers have been portrayed as intelligent enough to actually view human beings and interpret the motions and gestures of the human beings without the assistance of reflective tags or other markers. However, such scenes are created using special effects in which an actor carefully plays along with a predetermined movement script that makes it seem as if the actor is controlling the computers scripted actions. The actor is not actually controlling the computer, but rather attempting to create the illusion of control.